1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to detecting a malfunctioning speaker, and more particularly, to determining whether a speaker is functioning properly or malfunctioning.
2. Description of the Related Art
Audio apparatuses process audio signals received from an external source or audio signals stored in recording media, and output sounds corresponding to the audio signals using a speaker. In general, audio apparatuses include a home theater, a television, a radio, a mobile phone and the like.
FIG. 1 is a block diagram illustrating a related art audio apparatus. With reference to FIG. 1, the audio apparatus includes a digital amplifier 110 which converts an audio signal into a pulse-width-modulation (PWM) signal and amplifies the signal, and a low pass (LC) filter 120 which performs LC-filtering high frequency components of the amplified PWM signal and outputs an analog audio signal to one or more speakers 130.
A sensor 140 senses the state of the digital amplifier 110, and a controller 150 turns off the apparatus if the sensor 140 senses that the digital amplifier 110 is in an abnormal state, such as excessive current or voltage, low voltage, abnormal temperature, and so on.
The frequency response of the digital amplifier 110 is determined according to the performance of the LC filter 120, and the LC filter 120 relates to the impedance of the speakers 130.
In general, the speakers 130 have an impedance of 4-8Ω, and general home audio apparatuses use speakers having an impedance of 8Ω. The LC filter 120 is designed to stabilize the frequency response of an audio frequency band in the impedance of the speakers 130.
FIG. 2 is a waveform showing the frequency response curve of an LC filter optimized to a general speaker having an impedance of 8Ω. As shown in FIG. 2, the audio frequency band 20 Hz-20 kHz has output frequency response at a regular level.
FIG. 3 is a waveform showing the frequency response of an LC filter when an impedance of 1Ω is connected to the LC filter optimized to a general speaker having an impedance of 8Ω. In FIG. 3, the frequency response in a high frequency area of 1 kHz-20 kHz is degraded. That is, the frequency response in a high frequency area of the LC filter 120 is affected by the impedance of the speakers 130.
In the related art audio apparatus, there is a method for preventing damage to the digital amplifier 110 by the sensor 140 sensing abnormalities in the digital amplifier 110. However, there is no method for protecting the speaker 130, which is more expensive than the digital amplifier 110.
For example, if the output of the digital amplifier 110 exceeds the rating, or a DC level is output, the speaker is not damaged within a short period of time but is slowly damaged over a long period of time. Accordingly, although the user may not notice the deterioration of the sound, the impedance of the speakers 130 is reduced but the output of the digital amplifier 110 is regular, so speakers 130 may occasionally catch fire due to overload.
Therefore, there is a need for methods to sense the state of the speaker 130.